Initial

resources/app/client/apps/sidebar/tabs/cards-directory.js

@@ -0,0 +1,21 @@
+/**
+ * The sidebar directory which organizes and displays world-level Cards documents.
+ * @extends {DocumentDirectory}
+ */
+class CardsDirectory extends DocumentDirectory {
+
+  /** @override */
+  static documentName = "Cards";
+
+  /** @inheritDoc */
+  _getEntryContextOptions() {
+    const options = super._getEntryContextOptions();
+    const duplicate = options.find(o => o.name === "SIDEBAR.Duplicate");
+    duplicate.condition = li => {
+      if ( !game.user.isGM ) return false;
+      const cards = this.constructor.collection.get(li.data("documentId"));
+      return cards.canClone;
+    };
+    return options;
+  }
+}